#15: One-On-One Wrist Ride & Hammerlock
Getting the opponent's arm behind his back is not the easiest of tasks, but when you can, it is extremely controlling. You may want to get this when riding Parallel Legs and your opponent doesn't allow you to get a power half.
When his arm is on his back, be sure to force it to the far hip. If you take the wrist off of his back or toward his shoulders the referee will stop the match because it's potentially dangerous.
One-On-One Wrist Ride
Hammerlock (Arm Behind Back)